Earlier, Bank of England governor Mark Carney warned food prices could rise between 5% and 10% if there was a disorderly Brexit.

Theresa May faces deep opposition in Parliament to the proposed deal.

Lord King wrote there had been three episodes in modern history when the British political class let down the rest of the country.

‘Madness’

“In the 1930s, with appeasement; in the 1970s, when the British economy was the ‘sick man’ of Europe and the government saw its role as managing decline; and now, in the turmoil that has followed the Brexit referendum.

“In all three cases, the conventional wisdom of the day was wrong.”

He said it would be “madness” to “align the country indefinitely with laws over which it has no influence” and that a second referendum “is vital to escape from this continuing nightmare”.

He also said it was “intolerable for the fifth largest economy in the world to continue indefinitely as a fiefdom”, which was what, he said the Brexit deal offered.

‘Not ready’ for WTO

In his Bloomberg article, Lord King said government preparations for Brexit based on trade under WTO terms should have started in 2016 immediately after the referendum, “as I said at the time”.

Mr Carney told MPs the UK’s ports were not ready for a no-deal Brexit that would see the country trade under WTO rules.

He said: “At this point in time, the ports are not ready for a move to an administered WTO relationship.

“To be absolutely clear, our agents, my colleagues, we have gone to these ports and had conversations directly with the ports in question. We have talked to the private logistics companies, so we have gathered direct information on this.”